Electronic devices containing active organic materials are attracting increasing attention for use in devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices. Devices containing active organic materials offer benefits such as low weight, low power consumption and flexibility. Moreover, use of soluble organic materials allows use of solution processing in device manufacture, for example inkjet printing or spin-coating.
An OLED device may comprise a substrate carrying an anode, a cathode and one or more organic light-emitting layers between the anode and cathode.
Holes are injected into the OLED device through the anode and electrons are injected through the cathode during operation of the device. Holes in the highest occupied molecular orbital (HOMO) and electrons in the lowest unoccupied molecular orbital (LUMO) of a light-emitting material present within the OLED device combine to form an exciton that releases its energy as light.
Within an OLED device, the light-emitting material may be used as a dopant within a light emitting layer. The light-emitting layer may comprise a semiconducting host material and the light-emitting dopant, and energy will be transferred from the host material to the light-emitting dopant. For example, J. Appl. Phys. 65, 3610, 1989 discloses a host material doped with a fluorescent light-emitting dopant (that is, a light-emitting material in which light is emitted via decay of singlet excitons).
Formation of the one or more organic layers of an OLED may be by deposition of materials used to form those layers from a solution in a solvent followed by evaporation of the solvent. Examples of suitable solution processing methods include coating methods such as spin-coating or dip-coating and printing methods such as inkjet printing or roll-to-roll printing.
In devices comprising multiple organic layers, a first deposited organic layer may be rendered insoluble by crosslinking prior to deposition of a further organic layer by a solution processing method in order to prevent dissolution of the first deposited layer by the solvent used in formation by solution processing of the further organic layer.
WO 2005/049689 discloses polymers comprising fluorene repeat units substituted with crosslinkable groups, including a double bond, a triple bond, a precursor capable of in situ formation of a double bond or a heterocyclic, addition polymerisable group. Benzocyclobutane (BCB) is disclosed as an exemplary crosslinkable group.
WO 2010/013723 discloses polymers comprising double bond groups and BCB groups.
Mariet et al, Tetrahedron 60, 2004, 2829-2835 discloses calculated formation energies for formation of xylylenes from corresponding benzocyclobutanes.
WO2012003485 and WO2012003482 disclose hole-transporting layers formed by reaction of hole-transporting compounds substituted with benzocyclobutane.